As services using wireless mobile communication systems have become highly diversified, there is a strong demand for new technologies that can efficiently support newly introduced services. As such, active efforts are underway to research and develop new schemes and technologies usable in wireless mobile communication systems.
Device-to-device (D2D) communication is a newly introduced technology enabling new types of communication services. Basically, D2D communication enables a user equipment (UE) to directly communicate with another UE in the vicinity thereof. D2D communication supports both D2D discovery, which permits one UE to discover other UEs in the vicinity, and direct communication, which permits the UE to directly communicate with a discovered UE.
Compared to existing cellular communication involving wireless networks and base stations, D2D communication enabling direct communication between UEs requires a smaller amount of radio resources and is more efficient in the usage of radio resources. As D2D communication enables one UE to discover another UE in the proximity, it permits the UE to directly provide necessary information to a desired UE. Hence, advertisement and social networking services (SNS) can be efficiently supported. Currently, active efforts are underway to support D2D technologies in the Long Term Evolution-Advanced (LTE-A) system.
Meanwhile, in D2D communication, multiple UEs scattered in a specific area may simultaneously transmit information to each other. In this case, when a D2D UE transmits data using randomly selected transmit power, in-band emission power caused by this transmission acts as non-negligible noise to other UEs other than a D2D UE trying to receive the data. Particularly, for a system in which D2D communication and wireless cellular communication coexist, it is necessary to clear up the problem that in-band emission power caused by signal transmission of one D2D UE may act as noise to cellular transmission of another UE.